Change History (2)

You can change the /category/ prefix to something else on the Permalinks page, However you cannot remove it entrely.

One of the major reasons (ok, the only reason) is the complexity of which that using %category% without a prefix causes in permalinks, WordPress has to list every single category in its rewrite rules, which on some blogs, can end up with thousands of rules..

If someone wishes to use it like you're asking for, I personally believe it should be handled by a plugin, and not by core, as its not really a very efficient way of handling requests.